1. Field of the Invention
The present invention relates to a transaction proof apparatus and method in which items on a transaction, such as the contents of the transaction carried on between at least two interested parties, are objectively proved by utilizing a communication network.
2. Description of the Related Art
Nowadays, with the popularization of the Internet and personal computers, various transactions are being carried on among computers through communication networks. Since, however, basically anybody is free to access the Internet, the identification of the person himself/herself of the opposite communicating party is difficult, and the surreptitious use and alteration of transmission data are also apprehended.
Therefore, contrivances for preventing such dishonest acts are indispensably required for making full-scale commercial dealings in a network environment. Prior-art methods of preventing dishonest acts include the following by way of example:
(a) Electronic Commerce System (Japanese Patent Application Laid-open No. S62-056043)
In creating his/her own digital signature (or electric signature or electronic seal impression), a signer affixes date data indicating the term of validity of the digital signature, to the predetermined position of data for certification. Thus, the signer clearly states the deadline for a reply, to a certifier who has received the digital signature. Concretely, he/she declares that, in the absence of the reply by the deadline, a commercial transaction shall be suspended, the transmitted digital signature being also invalidated.
In a case where the signer has not obtained the reply in spite of the expiration of the term of validity, he/she can invalidate the digital signature by reporting the fact to a notarizing agency together with the digital signature. Thus, even in a case where the certifier of the digital signature has run away with this signature without sending back the reply or where the certifier has transmitted the false signature, the misuse of the particular digital signature can be prevented.
(b) Electronic Notarization Method and Apparatus (Japanese Patent Application Laid-open No. H06-014018)
When an electronic notarization apparatus has been supplied with data from an interested party who desires the proof of the genuineness of the data, a date generator generates date information for appointing a certain point of time which the interested party cannot change. Subsequently, the contents of the data and the date information are encrypted by an encryptor, and the proved genuine data printed with the date are output from a notarization device. Thus, it is permitted to confirm that the missive (or document) or electronically recorded data has/have not been changed since the printed date, and to electronically notarize the genuineness of the missive.
The prior-art methods of preventing dishonest acts as explained above, however, involve problems as stated below.
According to the electronic commerce system, the term of validity of the digital signature can be notified to the opposite party of the transaction, thereby preventing the misuse of the signature. With this system, however, it is impossible to identify the opposite party of the transaction or to prevent the alteration of the contents of the transaction.
On the other hand, according to the electronic notarization method, the notarization apparatus can electronically notarize the genuineness of the missive by affixing the date information to this missive. Since, however, the notarization apparatus proves the genuineness of the data that has been input by the sole interested party, it cannot decide if the data has been altered before the input operation. Consequently, incorrect contents might be output as the genuine data in cases of the transaction missive etc. between two parties.
Accordingly, the known method has the problem that a malicious user might misrepresent transactional contents etc., so the commercial transaction utilizing the network is not always carried on with safety.
Meanwhile, transactions in a commodity exchange are administered in the following aspect: The transactions of commodities, such as forward bargains, are all carried on in the commodity exchange. The interested parties of the transactions become the members thereof, and they pay a predetermined amount of guaranty money beforehand. Herein, in a case where a malpractice has been committed, the guaranty money is confiscated.
The transactions in the commodity exchange, however, are different from the general transactions between enterprises and are difficult to direct applications to the commercial transactions on the network.
An object of the present invention is to provide a transaction proof apparatus and method with which the safety of a transaction to be carried on between at least two interested parties is guaranteed by utilizing a communication network.
A transaction proof system according to the present invention comprises a transaction proof apparatus and terminal devices which belong to first and second users. It will process information on a transaction which is carried on between or among a plurality of users. The transaction proof apparatus and each terminal device are interconnected by a communication network.
The first user""s terminal device creates the digital signature data of the first user for transaction document (or transaction missive) data which state items on the transaction between the first and second users, while the second user""s terminal device creates the digital signature data of the second user for the particular transaction document data. The digital signature data of the first and second users are respectively transmitted to the transaction proof apparatus through the network.
The transaction proof apparatus is equivalent to an information processing equipment belonging to a third party (or a disinterested party), and it includes a communication unit, a processing unit and a storage unit. The communication unit is connected to the network, and it receives the digital signature data of the first user and those of the second user from the network. The processing unit verifies the first user""s and second user""s digital signature data, while the storage unit stores them therein.
The digital signature of any user can be created solely by the user himself/herself. Therefore, when the user""s digital signature has been affixed to the transaction document data, the contents of the transaction are regarded as having been approved by the particular user.
Upon receiving the digital signature data through the communication unit, the processing unit decrypts the respective digital signature data by use of public keys belonging to the first and second users, and it verifies the contents of both the digital signature data.
If the contents of both the digital signature data are the same, the processing unit deems that both the first and second users have agreed on the transaction, and it retains these digital signature data in the storage unit as the evidence of the agreement. In contrast, if the contents of both the digital signature data are discrepant, the processing unit deems that the transaction has ended in failure, and it notifies an error to the first user""s and second user""s terminal devices.